1. Field of the Invention
The present invention relates to a hinge apparatus, and more particularly to a hinge apparatus that supports a cover of an image forming apparatus, such as a photocopier, a scanner, or a multifunction machine, so that the cover thereof pivotably opens and closes.
2. Description of the Related Art
An image forming apparatus, which has document scanning function like a photocopier, a scanner, or a multifunction machine, scans a document, then stores a scanned image as data, or prints the image on a printing paper. Such an image forming apparatus includes a document glass disposed on a main body of the image forming apparatus to scan the document, a cover to secure the document laid on the document glass, and a hinge apparatus connecting the cover and the main body of the image forming apparatus.
FIG. 1 shows a hinge apparatus 30 to open and close the cover of the conventional image forming apparatus 10, disclosed in Japanese Patent Publication No. 11305358. As shown in FIG. 1, the conventional hinge apparatus 30 includes a hinge body 32 integrally formed with a spring pin 31, and a spring 33 connected to the spring pin 31 at one end. A cover 20 is provided with a hinge pin 21 that is inserted into a long hole 32a positioned in the hinge body 32. The spring 33 is connected to the hinge pin 21, and therefore, the cover 20 and the hinge apparatus 30 form a set. A cam part 20a, which is disposed at the cover 20, is in tight contact with the hinge body 32 under a recovery force of the spring 33. Furthermore, the hinge body 32 is disposed to move upward and downward within a coupling hole 10a positioned in the main body of the image forming apparatus 10.
The conventional image forming apparatus with the above structure has a document glass 11, which is exposed and covered through pivoting of the cover 20 centering on the hinge pin 21. The cover 20 opens and closes slowly, since the cover 20 is moved with the cam part 20a of the cover 20 being in close contact with the hinge body 32. Moreover, when a thick document is laid upon the document glass 11, the hinge body 32 is lifted upward to a predetermined height, so that the cover 20 uniformly presses the document, such as a thick book, laid upon the document glass 11.
But in the above conventional hinge apparatus 30, there is a difficulty in assembling the cover 20 and the hinge apparatus 30, since the both ends of the spring 33 are directly connected with the cover 20 and the hinge body 32, that are respectively at an opposite side. In other words, the spring 33 has a high elastic modulus to secure a slow opening and closing of the cover is used, and accordingly it is not easy to connect the spring 33 with the spring pin 31 of the hinge apparatus 30 and with the hinge pin 21 of the cover 20.
Also, a friction between the cam part 20a of the cover 20 and the hinge body 32 generates a noise in opening and closing of the cover 20. Another problem is that the hinge body 32 can be released out of the coupling hole 10a of the main body of the image forming apparatus, when a thick document is being scanned.